The present invention relates to an optical prism which is used in an optical system for projecting image, produced on a liquid crystal or like image display, onto a viewer""s eye ball retina. Such an optical prism is a main optical element in an image display unit in a head mounted display (abbreviated HMD), in which the image display unit is held at a predetermined position by a frame member mounted on the viewer""s head for single- or double-eye image viewing.
Recently, development of such HMDs is in progress, and these devices are finding increasing applications in various fields, such as medical, construction and educational fields and also amusement field such as various game machines.
Meanwhile, there is a trend for developing VGA purpose devices which can display high quality images and also displays of data systems as a version of OA (office automation) systems.
Many HMDs having been developed or proposed up to date, are of double-eye viewing type having a left and right image display for the left and right eyes for viewing these image displays with both eyes. For OA purposes, on the other hand, HDMs of single-eye viewing type also have been proposed. Such an HMD permits a single eye to view an image display, while permitting a keyboard and other operating sections to be operated simultaneously using the other eye, forward and at-hand visual field thereof being ensured to this end.
The OA and like purpose HMDs are desirably compact and handy in construction, so that they can be worn for use in a sense just like wearing glasses.
However, HMDs for general home applications are stage of development, and no proposal has been made for a product, which is not only handy but also can sufficiently solve various specific technical problems posed in its manufacture.
Japanese Laid-Open Patent Publication No. 8-234147, for instance, shows an optical prism, which reflects reflected light from an incidence surface, having been incident from a display face of an LCD or like display, at least twice in itself before emitting the light from a predetermined emission surface to the outside such that the emitted light is led to a viewer""s pupil.
This optical prism is a one-piece member having a plurality of non-spherical reflecting surfaces, and satisfies various optical requirements even when constructed as a viewing system.
When constructing an HMD or the like by employing this optical prism, however, it is necessary to hold the optical prism and a liquid crystal display in a regular positional relation with high accuracy in order to obtain an accurate projection liquid crystal display image onto the viewer""s retina. It is an unsolved technical problem to ensure the positioning accuracy and also facilitate the manufacture.
The present invention was made in view of the above circumstances, and its object is to provide an optical system of the type as described, which can ensure necessary accuracy of the positioning of it and an image display to each other and also facilitate manufacture when it is employed as an optical element of OA and various other systems.
Features and advantages over the prior art of the present invention will be described in the following:
(1) According to a first aspect of the present invention, there is provided an optical prism for reflecting incident light from an incidence surface suited for incidence of light from a predetermined display or like light source for at least twice before emitting the reflected light as emission light through a predetermined emission surface. The optical prism has side surfaces crossing the incidence and emission surfaces and including receded surfaces formed such as not to impede an optical path of an effective size, the incident light being led along the optical path from the incidence surface to the emission surface.
Heretofore, no optical prism of this type has been proposed, which has a specific shape such as to permit size reduction of its entirety, including portions for positioning it and a display or the like relative to each other and also maintaining the relative positions of it and the display.
According to the present invention as in (1) above, the receded surfaces do not impede the optical path of the effective size, along which light from the display or like light source is led, and can be utilized for providing portions for positioning the optical prism and the display or the like to each other and maintaining the relative positions of these components. Besides, it is possible to provide portions which do not impede size reduction of the overall structure.
(2) According to a second aspect of the present invention, there is provided the optical prism according to (1), which is fabricated by an injection molding process, and in which the side surfaces have a die removal slope of 1 to 10 degrees with respect to a die removal direction in the injection molding process.
Heretofore, no optical prism of this type has been proposed, which has a specific shape suited for mass production.
According to the present invention as in (2) above, the optical prism has a specific shape which, in addition to the effect obtainable according to the present invention as in (1) above, is suited for mass production by an injection molding process.
(3) According to a third aspect of the present invention, the optical prism according to (1) is provided having projections outwardly projecting from the receded surfaces at a predetermined position thereof.
Heretofore, no optical prism of this type has been proposed, which has a specific shape which permits size reduction of its entirety even in the case where projections are provided as portions for positioning it and the display or the like and also maintaining the relative positions of these components.
According to the present invention as in (3) above, the receded surfaces do not impede the effective size optical path of light from the display or like light source, and can be utilized for providing projections serving as portions for positioning the optical prism and the display or the like relative to each other and also maintaining the relative positions of these components. Besides, the size reduction is less impeded by the projections even though these projections outwardly project from the receded surfaces.
(4) According to a fourth aspect of the present invention, there is provided the optical prism according to (3), which is fabricated by an injection molding process, and the projections of which have predetermined outer surface portions serving as eject pin contact surfaces in the injection molding process.
Heretofore, no specific means in the optical prism has been proposed that sets eject pin contact surfaces when fabricating the optical prism of this type in an injection molding process.
According to the present invention as in (4) above, in addition to the effect obtainable according to the present invention as in (3) above, the eject pin contact surfaces concerning the pertinent injection molding process are set on predetermined portions of the projection surfaces. Thus, any push flaw by the eject pin in forced contact will not deteriorate the performance of the optical prism utilizing the optical properties thereof.
(5) According to a fifth aspect of the present invention, there is provided the optical prism according to (3), wherein the projections include frame portions for holding the display or the like and positioning portions for determining the position of the display or the like relative to the optical prism.
Heretofore, no optical prism of this type has been proposed, in which the projections do not impede the size reduction of its entirety even if they are utilized as positioning portions for determining the positions of a frame member supporting the display or the like and relative to each other.
According to the present invention as in (5) above, the projections which are provided by utilizing the receded surfaces, in addition to the effect obtainable according to the present invention as in (3) above, less impede the size reduction even if they are utilized as positioning portions for determining the positions of a frame member supporting the display or the like and the optical prism, because the extent of their projection can be controlled by the receded surfaces.
(6) According to a sixth aspect of the present invention, there is provided the optical prism according to (5), wherein the projections each have one or more flat portions, some of the flat portions being substantially parallel at a perpendicular to display mounting surfaces formed on the frame portions.
Heretofore, no optical prism of this type has been proposed, which has a specific structure for ensuring necessary accuracy of positioning of it and a display relative to each other.
According to the present invention as in (6) above, in addition to the effect obtainable according to the present invention as in (5) above, it is possible to readily ensure necessary accuracy of positioning of the optical prism and the display relative to each other.
(7) According to a seventh aspect of the present invention, there is provided the optical prism according to (5), wherein the projections have one or more flat surfaces, one of the flat surfaces being a positioning surface having a greater area than an opposite surface behind it, side surfaces defined between the positioning surface and the opposite surface being formed such that they have a predetermined die removal slope suited for injection molding in the fabrication of the optical prism.
Heretofore, no specific structure of this type has been proposed which permits readily ensuring necessary accuracy of positioning of the optical prism and the display relative to each other and also readily fabricating the optical prism by injection molding.
According to the present invention as in (7) above, in addition to the effect obtainable according to the present invention as in (5) above, it is possible to permit readily ensuring necessary accuracy of positioning of the optical prism and the display relative to each other and also readily fabricating the optical prism by injection molding.
(8) According to an eighth aspect of the present invention, there is provided the optical prism according to (5), wherein the positioning portions have protruding or receding portions corresponding to receding or protruding portions of a frame member of the display or the like, the protruding or receding portions of the positioning portions having protrusions or depressions for restricting the release of their engagement with the receding or protruding portions of the frame member at least in a particular direction.
Heretofore, no specific structure of this type has been proposed, which permits readily ensuring necessary accuracy of positioning of the optical prism and the display relative to each other and also readily assembling the two components.
According to the present invention as in (8) above, in addition to the effect obtainable according to the present invention as in (5) above, it is possible to permit readily ensuring necessary accuracy of positioning of the optical prism and the display relative to each other and also readily assembling the two components.
(9) According to a ninth aspect of the present invention, there is provided the optical prism according to (8), wherein the protrusion or depressions are formed as ant protrusions or ant notches corresponding to ant notches or ant protrusions as receding or protruding portions of the frame member.
Heretofore, no specific structure of this type has been proposed, which permits readily ensuring necessary accuracy of positioning of the optical prism and the display relative to each other and also readily assembling the two components.
According to the present invention as in (9) above, in addition to the effect obtainable according to the present invention as in (8) above, it is possible to permit readily ensuring necessary accuracy of positioning of the optical prism and the display relative to each other and also readily assembling the two components.
(10) According to a tenth aspect of the present invention, there is provided the optical prism according to (8), wherein the positioning portions have elastic force receiving surfaces in contact with and receiving elastic forces of elastic pieces, which are provided on the frame member such as to suppress displacement of the frame member relative to the positioning portions by elastic forces induced by their own elastic deformation.
Heretofore, no specific structure of this type has been proposed, which permits readily ensuring necessary accuracy of positioning of the optical prism and the display relative to each other and also readily assembling the two components.
According to the present invention as in (8) above, in addition to the effect obtainable according to the present invention as in (5) above, it is possible to permit readily ensuring necessary accuracy of positioning of the optical prism and the display relative to each other and also readily assembling the two components.
(11) According to an eleventh aspect of the present invention, there is provided an optical prism for reflecting incident light from an incidence surface suited for incidence of light from predetermined display or like light source for at least twice before emitting the reflected light as emission light through a predetermined emission surface, wherein: the optical prism has side surfaces crossing the incidence and emission surfaces and including receded surfaces formed such as not to impede an optical path of an effective size, the incident light being led along the optical path from the incidence surface to the emission surface, and predetermined areas of the receded surfaces being provided with a surface roughening treatment or like surface treatment.
Heretofore, no specific arrangement for effectively evading ghost generation due to light side-wise entering the effective size optical path in the optical prism from the incidence surface to the emission surface has been proposed.
According to the present invention as in (11) above, light is prevented from side-wise entering the effective size optical path in the optical prism from the incidence surface to the emission surface, thus preventing the image viewing quality from being spoiled by ghost effects.
(12) According to a twelfth aspect of the present invention, there is provided the optical prism according to (11), which is fabricated by an injection molding process, in which the surfaces provided with the roughening surface treatment or like surface treatment have a die removal slope of 3 to 20 degrees with respect to a die removal direction in a pertinent injection molding process.
Heretofore, no specific proposal of this type was made, which permits improving the processibility of fabrication of the optical prism by an injection molding process.
According to the present invention as in (12) above, in addition to the effect obtainable according to the present invention as in (11) above, it is possible to improve the processibility of fabrication of the optical prism particularly in an injection molding process.
(13) According to a thirteenth aspect of the present invention, there is provided an optical prism for reflecting incident light from an incidence surface suited for incidence of light from predetermined display or like light source for at least twice before emitting the reflected light as emission light through a predetermined emission surface. The incidence and emission surfaces and also the reflecting surfaces concerning the reflection are subustantially quadrilateral as defined by their edges.
Heretofore, no specific proposal of this type has been made, which permits ensuring necessary die processing accuracy when fabricating the optical prism by an injection molding process.
According to the present invention as in (13) above, it is possible to permit readily ensuring necessary die processing accuracy when fabricating the optical prism by an injection molding process and thus readily ensuring necessary processing accuracy of the optical prism itself.
(14) According to a fourteenth aspect of the present invention, there is provided an optical prism for reflecting incident light from an incidence surface suited for incidence of light from predetermined display or like light source for at least twice before emitting the reflected light as emission light through a predetermined emission surface. The optical prism is fabricated by an injection molding process, and a reference axis of either one of the incidence surface, emission surface and reflecting surfaces and a die removal direction in a pertinent injection molding process are substantially parallel to each other.
Heretofore, no specific proposal of this type has been made, which permits improving the processibility of fabrication of the optical prism by an injection molding process.
According to the present invention as in (12) above, in addition to the effect obtainable according to the present invention as in (11) above, it is possible to improve the processibility of fabrication of the optical prism particularly in an injection molding process.
(15) According to a fifteenth aspect of the present invention, there is provided an optical prism for reflecting incident light from an incidence surface suited for incidence of light from predetermined display or like light source for at least twice before emitting the reflected light as emission light through a predetermined emission surface. The optical prism is fabricated by an injection molding process, and a die split line in the injection molding process does not pass through the incidence and emission surfaces, the reflecting surfaces and the edges of these surfaces except for the edge defining the incidence and emission surfaces adjacent to each other and the edge defining the reflecting surfaces adjacent to each other.
Heretofore, there has been no specific means for avoiding size increase of the optical prism while ensuring the effective optical size thereof when fabricating the optical prism by an injection molding process.
According to the present invention as in (15) above, a die removal slope when fabricating the optical prism by an injection molding process is provided on two optical surfaces with respect to a die split line, and it is thus possible to avoid size increase of the optical prism while ensuring the effective optical size.
(16) According to a sixteenth aspect of the present invention, there is provided an optical prism for reflecting incident light from an incidence surface suited for incidence of light from a predetermined display or like light source for at least twice before emitting the reflected light as emission light through a predetermined emission surface. The optical prism is fabricated by an injection molding process, and a die split line concerning the injection molding process passes through projections outwardly projecting form side surfaces crossing the incidence and emission surfaces and formed at adequate transversal positions.
Heretofore, no specific structure of this type has been proposed, which is suited for forming, when fabricating the optical prism by an injection molding process, portions for positioning the optical prism and the display or the like relative to each other and also maintaining the relative positions of these components.
According to the present invention as in (16), it is possible to readily form, when fabricating the optical prism by an injection molding process, the portions for positioning the optical prism and the display or the like relative to each other and also maintaining the relative positions of these components.
(17) According to a seventeenth aspect of the present invention, there is provided the optical prism according to (16), wherein the projections have positioning regulation portions formed in their predetermined portions and for regulating the positioning of a frame member supporting the display or the like, the die slit line passing through predetermined surface portions of the positioning regulation portions.
Heretofore, no specific structure has been provided, which can ensure a sufficient area as a predetermined area of a positioning regulation portion for regulating the positioning of a frame member supporting the display or the like.
According to the present invention as in (17) above, in addition to the effect obtainable according to the present invention as in (16) above, the predetermined area of the positioning regulation portion for regulating the positioning of the frame member supporting the display or the like, is not restricted by the die removal slope necessary for fabricating the optical prism by an injection molding process, and it is thus possible to readily ensure a sufficient area.
(18) According to an eighteenth aspect of the present invention, there is provided the optical prism according to (17), wherein predetermined surface portions of the projections other than the positioning regulation portions are set as eject pin contact surfaces concerning a pertinent injection molding process.
Heretofore, no specific proposal of how to set an eject pin contact surface concerning a pertinent injection molding process has been made.
According to the present invention as in (18) above, a predetermined portion of the projection surface is set to be an eject pin contact surface in the pertinent injection molding process, and even a push flaw produced by the eject pin in forced contact will not deteriorate the performance of the optical prism utilizing optical properties thereof.
(19) According to a nineteenth aspect of the present invention, there is provided the optical prism for reflecting incident light from an incidence surface suited for incidence of light from a predetermined display or like light source for at least twice before emitting the reflected light as emission light through a predetermined emission surface. The incidence and emission surfaces and the reflecting surfaces as optical surfaces have flat surfaces of 1 millimeter or more in diameter formed outside effective size areas.
Heretofore, no specific proposal of the structure permitting measurement for ensuring the accuracy of the shape and dimensions of the optical prism has been made.
According to the present invention as in (19) above, the angular eccentricity of each optical surface of the optical prism can be measured by utilizing the flat surfaces of 1 millimeter or more formed outside the effective size areas. It is thus possible to ensure necessary accuracy of the shape and dimensions of the optical prism according to data of measurements.
(20) According to a twentieth aspect of the present invention, there is provided an optical prism for reflecting incident light from an incidence surface suited for incidence of light from predetermined display or like light source for at least twice before emitting the reflected light as emission light through a predetermined surface. Portions including predetermined portions having Imaginary edges defined between adjacent imaginary surface portions of the incidence and emission surfaces adjacent to each other, and the reflecting surfaces adjacent to each other, except for effective size areas of these surfaces, are chamfered.
Heretofore, no specific structure of this type has been proposed, which permits minimizing the size and weight of the optical prism.
According to the present invention as in (20) above, it is possible to yet minimize the size and weight of the optical prism.
(21) According to a twenty first aspect of the present invention, there is provided the optical prism according to (20), which is fabricated by an injection molding process, and in which a die split line concerning the injection molding process passes through the chamfered portions.
Heretofore, no specific structure of this type has been proposed, which permits minimizing the size and weight of the optical prism.
According to the present invention as in (20) above, it is possible to yet minimize the size and weight of the optical prism.
(22) According to a twenty second aspect of the present invention, there is provided an optical prism for reflecting incident light from an incidence surface suited for incidence of light from predetermined display or like light source for at least twice before emitting the reflected light as emission light through a predetermined emission surface. Pertinent ones of the incidence and emission surfaces and reflecting surfaces as optical surfaces have indexes formed at predetermined positions or optical on optical axis.
Heretofore, no specific proposal of the structure permitting measurement for ensuring the accuracy of the shape and dimensions of the optical prism has been made.
According to the present invention as in (22) above, the indexes can be utilized for measuring the position relation and angular eccentricity of the optical surfaces of the optical prism. It is thus possible to ensure the accuracy of the shape and dimensions of the optical prism according to data of measurements.